This invention relates to a rocking bearing for rockably supporting a movable part such as a swash plate mounted in a swash plate type, variable-capacity plunger pump or a swash plate type hydraulic motor.
Generally, in a swash plate type plunger pump, as shown in FIG. 5, a rocking bearing B1 is mounted between a concave arcuate surface 2 formed on a housing 1 and a convex arcuate surface 4 formed on a swash plate 3 to rockably support the swash plate. By adjusting the inclination of a flat plunger guide surface 5 by the rocking of the swash plate 3, the stroke of a plunger 8 inserted in a cylinder 7 of a cylinder barrel 6 is adjusted to adjust the discharge amount.
As the rocking bearing B1 for rockably supporting the swash plate 3, one has been used which comprises an arcuate bearing ring 40 along the arcuate surface 2 of the housing 1, an arcuate retainer 42 mounted along a raceway 41 formed on the inner periphery of the bearing ring 40, and rolling elements 44 housed in pockets 43 of the retainer 42.
With such a known rocking bearing, the cost of the rocking bearing was high because the bearing ring 40 was a member formed by cutting.
If the rocking bearing B1 is merely mounted between the arcuate surface 2 of the housing 1 and the arcuate surface 4 of the swash plate 3, the entire rocking bearing B1 or the retainer 42 will displace in a circumferential direction with inclination adjustment of the plunger guide surface 5 or due to vibration during operation of the plunger pump. This makes it impossible to support the swash plate 3 with good stability.
Heretofore, between the housing 1 and the bearing ring 40, a pin hole 45 is formed in the housing 1 and a pin 46 is mounted in the bearing ring 40 to keep the bearing ring 40 in position by the engagement of the pin 46 in the pin hole 45.
Also, a rest arm 47 is provided between the housing and the swash plate 3, and part of the rest arm 47 is inserted in a cutout 48 formed in the retainer 42 to prevent circumferential displacement of the retainer 42.
But, the pin 46 as the positioning means for the bearing ring 40 and the arm 47 as the means for limiting the amount of rocking of the retainer 42 increases the number of parts and it is troublesome to mount the pin 46 or rest arm 47. Also, in order to mount the pin 46, a hole for the pin has to be formed in the bearing ring 40. Further, since the cutout for inserting the arm 47 has to be formed in the retainer 42, the machining cost is high.
A first object of this invention is to reduce the manufacturing cost of a rocking bearing.
A second object of this invention is to improve the ease of mounting of the rocking bearing.
According to this invention, there is provided a rocking bearing comprising a support member formed with a concave arcuate surface, a movable member formed with a convex arcuate surface, an arcuate bearing ring mounted between the concave arcuate surface formed on the support member and the convex arcuate surface formed on the movable member, an arcuate retainer mounted inside of the bearing ring so as to extend along an arcuate raceway formed on the inner periphery of the bearing ring and formed with a plurality of pockets, and rolling elements received in the pockets of the retainer for rockably supporting the movable member, characterized in that the bearing ring is formed by pressing a steel plate.
By forming the bearing ring by pressing a steel plate, it is possible to reduce the cost of the rocking bearing and to achieve light weight and compactness of the rocking bearing.
As the steel plate, SCM or SPCC may be used. The press-formed bearing ring is subjected to heat treatment after pressing to increase hardness. If strains develop during heat treatment, the rolling elements cannot smoothly roll. Thus, heat treatment is preferably carried out with the bearing ring in a mold.
According to this invention, by providing a rocking amount limiting means for limiting the rocking amount of the retainer between the bearing ring and the retainer, it is possible to prevent the retainer from shifting and dropping.
As the rocking amount limiting means, by providing engaging pieces bent inwardly from both ends of the bearing ring so as to oppose both ends of the retainer with a spacing therefrom to limit the rocking amount of the retainer, it is possible to eliminate the necessity for parts for limiting the rocking amount such as a rest arm. Thus, it is possible to reduce the number of parts of the rocking bearing and improve assembling properties.
By providing means for positioning the bearing ring relative to the support member between the support member and bearing ring, it is possible to prevent shifting of the bearing ring.
As the positioning means, one may be used in which L-shaped engaging pieces bent outwardly from both ends of the bearing ring are formed and the tips of the engaging pieces are engaged in positioning holes formed in a flat surface of the support member, or one in which positioning claws cut and raised from both ends of the bearing ring toward an outer surface side and the positioning claws are engaged in positioning recesses formed at both ends of the arcuate surface of the support member. In another embodiment, a protrusion is formed on the outer peripheral surface of the bearing ring by embossing, and the protrusion is engaged in a positioning hole formed in the arcuate surface of the support member.
Since in any of these positioning means, the positioning pieces, claws or protrusion are integrally provided, it is not necessary to mount additional parts for positioning. Thus it is possible to reduce the cost and improve ease of assembling of the rocking bearing due to a reduced number of parts.
Other features and objects of the present invention will become apparent from the following description made with reference to the accompanying drawings, in which: